RELATIONSHIPS OF PROTEIN COMPOSITION AND DOUGH RHEOLOGICAL MEASUREMENTS WITH BREADMAKING PERFORMANCE OF WHEAT FLOURS

Abstract

Protein and ash content, rheological properties, protein composition and baking performance of twenty two wheat flours (Triticum aestivum L.) grown in the Center-Western of the United States of America during the year 2000, were determined. Rheological properties were evaluated with the National mixograph, Brabender farinograph and extensigraph, Chopin alveograph, and the texture analyzer TA-XT2. The relative amounts of polymeric and monomeric proteins were determined in SDS-buffer extracts separated by SE-HPLC. The baking quality (bread loaf volume) of the flours was evaluated by a straight dough baking procedure. The relationships among protein composition, rheological properties, and loaf volume were evaluated. The proportion of unextractable polymeric protein, both in the total protein (PPNET) and in the flour (PPNEH), was the fraction that correlated better with most of the rheological measurements [TdMix (r=0.6** and 0.6**), alveograph L (r=0.5* and 0.7**) and W parameters (r=0.2 and 0.5* ), extensigraph Rmax (r=0.4** and 0.7**) and work of deformation (r=0.5** and 0.7**), TA-XT2 maximum resistance (r = 0.4** and 0.4**) and deformation work (r=0.3** and 0.4**)], followed by albumins/globulins [TdMix (r=-0.5**), W (r=-0.7* ), extensigraph maximum resistance (r=-0.5**) and deformation work (r=-0.6* ), TA-XT2 maximum resistance (r=-0.4* ) and deformation work (r=-0.5**)]; whereas gliadins showed no significant correlations. Bread loaf volume was positively correlated with Rmax, TdFar, stability, L, W, extensigraph deformation work, PPH, and PPNEH, but negatively with extensibility, and farinograph water absorption and mixing tolerance index (ITA). A prediction model for bread loaf volume was obtained which explains 87 % of the variation in loaf volume.